Studies will be performed on premature infants and infants of diabetic mothers to determine the value of the fatty acid composition of lecithins from amniotic fluid or gastric lavage at birth in predicting the risk of development of RDS in contrast to the L/S ratio. Serial measurements of tracheal wash lecithin fatty acid composition will be evaluated as to their usefulness in guiding management of infants with RDS. Similar studies will be carried on tracheal washings of adult patients with RDS following severe trauma or head injury in an attempt to determine whether altered surfactant lecithin composition plays a role in the development of pulmonary dysfunction in such subjects. Other experiments will examine the effects of essential fatty acids deficiency upon lecithin secretion by lung tissue in vitro. Experiments will also be performed to examine surfactant lecithin synthesis in type II cells grown in tissue culture from control and EFA deficient rats using various labelled precursors.